/sci/ - Science & Math

>>7710129
>we have never managed a manned hovering aircraft aside from the bulky, dangerous and hard to control helicopter.

https://en.wikipedia.org/wiki/List_of_VTOL_aircraft

>>7710129
Basic answer: It requires a lot more power to achieve decent lift.

Wings and fan blades are basically* the same thing: Airfoils that direct air downwards** to create lift. You may notice that the wings of an airplane are much, much, much larger than those fan blades, which means that they can direct a much larger mass of air downwards. This means that, in order to maintain the same upwards thrust, you need the downward airstream to be at a much higher velocity. (In other words, you have to spin the fan blades a lot faster.)

To put it in terms of high school physics, thrust is proportional to mass flow rate and the velocity of the airstream (p = mv, F = dp/dt) and power is proportional to mass flow rate and the square of velocity (E = 1/2 mv^2, P=dE/dt). So if you cut the mass flow in half, power has to go up 4x to maintain the same thrust.

And unlike wings, you will fall down immediately when the power is cut - whereas with wings, if the engines go off, your wings are still moving through the air at mostly the same velocity because of your plane's inertia, and so continue to direct air downwards, allowing you to glide to the ground safely.

Helicopters work because they have fairly large blades, but they're still limited to much lower altitudes than airplanes are, and have much lower efficiency. (They do, however, have the ability to glide back down as well - the air flowing over the blades when they fall also creates drag by turning the blades, slowing the fall enough that crashes are often survivable.)

Vehicles of this type *do* exist, and have been successfully built, but because they're less efficient they're not really used. With one exception - if your vehicle's basically plane-shaped, you can mount the engines on a revolving joint and lift off with them pointing down, and then point them backwards and fly efficiently like a plane the rest of the way.

*oversimplifying
*still oversimplifying

>>7710129
they aren't hard to control if you know what you're doing. And lets face it, do you want people that don't know what they're doing hovering above the general public?

>>7710129
High disk loading --> low efficiency

>>7710313
I hate this argument so much. Airspace is much more conductive to automatic transport than the ground is. They already have autonomous drones. Imagine autonomous air-taxis that you hopped into and it took you across a large city in 5 minutes? Currently to get across London takes about 2 hours on a bad day, imagine just being able to skip across 40 miles of traffic in a flying car?

>>7710129
Because you need to use EM Drives, not fans.

>>7710351
this